docs: def load_plugins():
          """
          Load all availabe plugins.
  
          Returns
          -------
          plugin_cls : dict
              mapping from plugin names to plugin classes
          """
          plugin_cls = {}
          for entry_point in pkg_resources.iter_entry_points('docker_interface.plugins'):
              cls = entry_point.load()
              assert cls.COMMANDS is not None, \
                  "plugin '%s' does not define its commands" % entry_point.name
              assert cls.ORDER is not None, \
                  "plugin '%s' does not define its priority" % entry_point.name
              plugin_cls[entry_point.name] = cls
          return plugin_cls